PHOENIX -- NOAA's Climate Prediction Center just released its winter outlook, but it's going to be a little harder to forecast due to the lack of El Niño.

El Niño is a weather phenomenon where the equatorial Pacific waters warm to above-average conditions.

During El Niño (warmer-than-average waters) or La Niña (cooler-than-average waters), the winter outlook is a bit easier for long-range forecasters to pinpoint. This year was expected to be an El Niño year but it has not developed and the window is closing.

“This is one of the most challenging outlooks we’ve produced in recent years because El Niño decided not to show up as expected," Mike Halpert, deputy director of NOAA's Climate Prediction Center. "In fact, it stalled out last month, leaving neutral conditions in place in the tropical Pacific.”

During El Niño years, forecasters have a better idea of what to expect. Right now, the winter outlook is calling for a warmer-than-average winter for the West this season.